adsoption absorption cracking

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ADSORPTION

ABSORPTIONCRACKING



ADSORPTION

Preferential partitioning of substances from the

gaseous or liquid phase onto the surface of a

solid substrate is Called Adsorption

Distillation : Relative volatility

Absorption: Solubility

Extraction: Distribution Coefficient

Adsorption: Pore diameter

Examples of Uses of Adsorption:

a. Removal of CO, CO2, CH4 from Hydrogen in PSA Unit

b. Use of desiccant to prevent corrosion in sparestrans ortation



Adsorbents – Desirable

Properties

Should have large internal surface areaAdsorbent should be regenerableShould not age easily

Mechanical Strength

Pore size

Adsorption - Surface Phenomenon -van der Waals forces and

electrostatic forces between adsorbate molecules and the

atoms which compose the adsorbent surface. Thus

adsorbents are characterized first by surface properties suchas surface area and polarity.



Absorption

The process of removal of one or more selectedcomponents from a mixture of gases into suitable liquid

by interphase mass transfer controlled largely by

rate of diffusion.



Absorption - type

Absorption - Physical

Absorption - Accompanied by Chemical Reaction

Example : Absorption of H2S in water

Absorption of H2S in MDEA

Depends upon solubility of solutes to be removed in liquidNo chemical reaction

Little heat released

Depends on chemical reaction of solute with liquid

Significant heat release

(CH2OHCH2)2NCH3 +H2S (CH2OHCH2)2NSCH3



Equipment

Plate Tower

Packed Tower

Type of Trays

DowncomerDistributor pipe

Packing support plate

Packing

Redistribution of liquid



Cracking

Cracking is the process of decomposition of high

molecular weight hydrocarbons to more valuable

lower molecular weight hydrocarbon.

Types : a. Thermal

b. CatalyticFixed bed

FCCMoving Bed



Thermal Cracking

Thermal Cracking is defined as the thermal decomposition,

under pressure, of large hydrocarbon molecules to form

smaller molecules

C10H22 C8H17 ° + C2H5°

C2H5° + C6H14 C2H6 + C6H13°

C6H13° C5H10 + CH3°C8H17° C4H8 + C4H9°

CH3° + H° CH4

C4H9° C4H8 + H°

Large Molecules decompose into smaller :

Free radicals react with other molecules to form sat HC & FR.

Termination of chain reaction :



Thermal Cracking

Vacuum

Flasher

Surge Drum

PC

TC

Fuel

FC FC

Thermal

Residue

Visbreaking Residue

Steam

PC

Sour Water

Thermal Cracked Naphtha

LongResidue

TC

PC

TC



Thermal Cracking -Salient

Features

Design of all equipment is to minimize coke formation

Heaters : tube diameter, Charge stock velocities, Heating rate

Temperature, Metallurgy, Coke prevention,Zone temperature control.

Soak Drum Gas oil stream is frequently used to wet the walls

of soak drum to prevent coke accumulation.

Use of stand by drum.

Pumps Should be able to handle high temp, corrosive liq.



Fixed Bed Catalytic Cracking

Charge

Heater

Turbo Compressor

Air Heater

Heat Exchanger

Heavy CatalytGas Oil

Light

CGO

Motor

Gasoline

to

Stabilizer

Wet Gas to

Stabilizer

Fresh Air

Spent Air



Moving Bed Catalytic Cracking

Reactor

Kiln

Flue Gas

Steam

Lift Engaging Hopper

Elutriator

Lift Disengaging Hopper

F r e s h C a t a l y s t

S t o r a g e

Steam

BFW

Purge Steam

Reactor Product



Fluidized bed Catalytic Cracking

Objective : To convert heavy fuel components into high-octane

motor gasoline blending components.

By products: Coke, C4 feed.

Interface with other Units: Overhead gas

Gasoline

BottomsProcess Description

Health, Safety, Environment & Fire (HSEF)



FCC - Process Flow

Flue Gas to PRTReactor

Stripper Debutanizer

LPG to

Merox

105-180 Naph toHNUU / Heavy

Mogas header

155-180 Naph

to Reactor

Naphtha

Splitter

C5-105 Naph. to

LNUU / Merox

C6-105 Naph. to

LNUU / Light

Mogas header

Depentanizer

C5 to SHP /

LNUU

C6-105 Naph.to LNUU

Deisohexanizer

i-C6

to Light

Mogas header

C7-105 Naph.

to Riser

Compressor

HP

Receiver

MC ovhd liquid

Primary

Absorber

Rich

Oil

Sponge

Absorber

Rich

Amine

to ATU

Lean

Amine

fr ATU

Treated Gas

to FG System

HP Liquid to Stripper

Lean

Oil

Amine

Absorber

Receiver

FLUIDIZED CATALYTIC CRACKING UNIT

3rd

stg

sep.

Orifice

Chamber

ExpanderSteam

Turbine

Motor/

Generator

Flue Gas Cooler

BFWHP

Steam

Stack

Process Air to Rg

Air

Raw oil

Rx

Vapors

1

10

26

Heavy cracked Naphtha

Product (180-215 °C)/

Heavy Mogas header

Heavy Naphtha (155-215°C)to Reactor

42

MP

Steam

1

6

6

1

Light Cycle Oil Product to

Diesel Blending System

MP

Steam

Main

Column

Light

Cycle

Oil

Stripper

Heavy

Naphtha

Stripper

Reflux

Drum

Fuel Oil Product to

FO System

MC ovhd vapor

M ai n A i r

Blower

Fuel

Gas Process

Air

Combu-

stor

Regenerator

Stripper

Riser

Regenerated

Catalyst

Spent

Catalyst

To Recovered Cat. Hopper

4th

stg.

sep.

546 oC

714 oC

121 oC1.55 Kg/cm2g

2.34 Kg/cm2g



Hydrocracker

Objective : To convert fuel oil components into Naphtha,

Kerosene, and gas oil

Interface with other Units: Feed Stock

Hydrogen comes from HMU

LPG

Naphtha

KeroseneProcess Description

HSEF



Hydrocracker - Process Flow

TC

Fist Stage

ReactorrSecond

Stage

Reactorr

High

PressorSeparator

Fractionation

PC

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